High-frequency generator



Nov. 7, 1950 A. MONTANI HIGH-FREQUENCY GENERATOR Filed Sept. 24, 1945FIG. I

m nzbo FIG. 2

INVENTOR.

ANGELO MONTANI ATTORN EY Patented Nov. 7, 1950 UNITED STATES TENT OFFICEHIGH'-FREQUEN CY GENERATOR Application September 24, 1945, Serial No.618,353

3 Claims.

The present invention relates to space discharge devices, andparticularly to space discharge devices of the electron beam type.

It' has heretofore been proposed to produce oscillating currents bymeans of a cathode ray beam which is caused to scan a mask having aseries of perforations, or apertures, therein, and collecting theelectrons which pass through the perforations on a collector anodepositioned behind the mask. The stream of electrons is interrupted bythe mask and consequently the col lector supplies a number of impulseswhose frequency depends upon the velocity of the beam movement and thenumber of apertures.

It is an object of the present invention to provide an improved spaceddischarge device of the electron beam type for :producing oscillatingcurrents having any desired waveform.

Another object of the'invention is to provide an improved spaceddischarge device of the electron beamtype for efiecting a multiplicationin the frequency of an alternating current.

Briefly, these objects are accomplished by providing a collectingelectrode and a mask in a tube structure similar to a conventionalcathode ray tube. The mask is preferably constructed in the form of agrid having interstices which vary in size in a predetermined manner.The mask is scanned by the cathode ray beam causing a current whichvaries in accordance with variations in the size of the interstices inthe mask to be produced therein. A complementary current is produced inthe collecting electrode, located behind the mask, by the electronspassing through the interstices. fication of the invention the mask isformed by two intersecting groups of parallel wires, the intersticesbetween the wires in each group varying progressively in a predeterminedmanner. With this mask more complex output currents may be obtained bydeflecting the cathode ray beam both horizontally and vertically. In asecond modification of the invention a ring-shaped mask is used havinginterstices about the circumference thereof which recurrently vary insize-in a continuous manner. When this mask is scanned by a rotatingcathode ray beam an alternating current having a frequency which is amultiple of the scanning frequency will be produced in the mask and inthe collecting electrode.

The invention will be better understood from the fOllOWil'lg descriptionwhen considered in conjunction with the accompanying drawing, in which:

Fig. 1 discloses one form of the invention in According to onemodi- 1which the electron beam is cyclically deflected along a rectilinearscanning path;

Fig. 2 is a modification of Fig. l in which the electron beam isdeflected in two directions; and

Fig. 3 is a modified form of mask forusein the tube shown in Fig. 2.

Referring to Fig. 1 of the drawing, there is shown a cathode ray tubehaving the conventional heater l, cathode 2, and beam forming electrodes3, t, and 5, all of which are energized-by a suitable battery 5, or thelike. The. pencillike electron beam, indicated by the broken line '1,passes between a pair of deflecting electrodes 3, which are positionedon opposite sides of the beam axis. It is to be understood that theequivalent magnetic deflecting coils or other suitable means may besubstituted for the electrostatic deflectin electrodes, if desired. Theelectron beam is caused to scan a. rectilinear path along the length ofmask 9' by applying an alternating voltage from a suitable source, suchas an oscil lator ill, to the deflecting electrodes 8. The mask 9 mayconveniently be constructed in the form of a pair of spaced apartarcuate supporting rods, which arebridged by a number ofparallel spacedapart wires in the manner of ladder rungs. The spacing of the bridging.wires varies along the length of the arcuate supporting rods in a mannerdependent upon the output waveform de-' sired. Several successive cyclesof such variations in the interstices may be used, if desired. Locatedbehind the mask 9 is a collecting electrode or plate, 12, upon whichelectrons passing through the mask 9 impinge. The mask 9 and thecollecting electrode l2 are connected to battery 6 through resistorsl3and [4, respectively, across which the output voltages are obtained whenthe tube is in operation. As the electron beam travels-from the top tothe bottom-of mask 5 a progressively smaller portion of the electrons inthe beam will be intercepted by'the mask and a progressively largerportion of the electrons will pass through the mask etc impinge on thecollecting electrode l2. On the return sweep of the electron beam theconverse action takes place.

Undulating currents are thus caused to flow through resistors l3 and 14,which may be bridged by small condensers l5 and [6, respectively, tosmooth out the waveform of the voltage appearing thereacross.

In Fig. 2 an additional pair of deflecting electrodes ll are provided todeflect the electron beam l in the horizontal plane under the control ofa second oscillator H. The mask or grid, l8 may in this case beconveniently formed by two groups of parallel spaced apart wires, thewires in the two groups intersecting at right angles. The grid mayconform to the surface of a sphere with center at a point on the axis ofthe tube between the pair of deflecting plates 8 and [1, as illustrated,to eliminate distorting effect which may otherwise be introduced whenthe electron beam is deflected large amounts. The spacin between thegrid wires in each group is varied progressively across the mask. Witheither one of the oscillators or H inactive, the tube shown in Fig. 2operates the same as that shown in Fig. 1. When both of the oscillatorsl0 and II are active, however, very complex waves may be produced by thetube shown in Fig. 2. The wave shape of the output Voltage obtainedacross resistors l3 and [4 may be varied by changing the amplitude orthe frequency of either one of the oscillators ID or H with respect tothe other. These two oscillators may be interlocked by means of wellknown synchronizing methods.

In Fig. 3 there is shown a circular mask which may be used in the tubeshown in Fig. 2 in place of mask I8 in order to adapt the tube for useas a, frequency multiplier. The mask 20 may comprise a disk 2! andconcentric ring 22, between which a number of grid wires, such as 23,extend in radial directions. The grid wires are located so as to providea plurality of closely spaced areas between which the spacing variesprogressively to a maximum value. Two such cyclic variations in spacinghave been shown in Fig. 3. If the two oscillators l0 and II are adjustedto the same frequency with their outputs in phase quadrature theelectron beam 1 will scan a circular path on the mask 20. It ispreferable to use only one oscillator and to provide a suitable phaseshifting network in order to obtain the necessary quadrature relationbetween the horizontal and vertical deflecting voltages. When theelectron beam 1 scans a circular path on the grid wires of the mask 20,a current having a frequency twice that of the scanning frequency willbe produced therein by the electrons intercepted thereby. A similarcurrent will be produced in the collecting electrode or plate, H! by theelectrons impinging thereon which pass through the mask 20. A greaterfrequency multiplication factor may be obtained by increasing the numberof cyclic variations in the spacing of the grid wires in the mask 20. Itshould be noted that this device provides a substantially continuousflow of energy to the output circuit instead of depending upon shockexcitation of a resonant circuit by impulses created by a commutatedelectron beam. The output frequency may therefor be varied by adjustingthe scanning rate without the need for any readjustment of tunedcircuits in the output circuit as in prior electron beam frequencymultipliers.

While what is now considered to be the preferred form of the inventionhas been illustrated, it is to be understood that numerous modificationsmay be incorporated therein without departing from the true spirit andscope of the in- 6 vention as defined in the subjoined claims.

What is claimed is:

1. A high frequency generator comprising an electron gun having a heatercathode, and forming electrodes, means for activating said electron gun,means for deflecting a projected stream of electrons in a fixed path, acollector anode located in said path, and a mask located in said pathbetween said electron gun and said anode for screening a stream ofelectrons deflected in said path towards said anode, said maskconsisting of a screen having a plurality of openings of variable areasfor correspondingly varying the intensity of a stream of electronsdeflected in said path and projected upon said anode through saidopenings of said mask, said openings of said mask occurring in at leasttwo sequential series, the areas of the openings in each said seriesvarying progressively from an area of minimum value to an area ofmaximum value accordin to a definite pattern.

2. In a high frequency generator, the combination with an electrondischarge device having means for emitting a beam of electrons, andhorizontal and vertical beam deflecting means for deflecting an emittedbeam of electrons in a closed two-dimensioned path, of a collectorelectrode positioned in said path and a grid positioned in said pathbetween said first means and said collector electrode for screening anemitted beam of electrons deflected in said path towards said collectorelectrode, said grid comprising a screen having a plurality of openings,said openings varying in size progressively in two intersectingdirections according to a predetermined pattern for correspondinglyvarying the intensity of an emitted beam of electrons deflected in saidpath and projected upon said collector electrode through said openingsof said grid.

3. In a high frequency generator, a cathode, a plate, means for formingan intensified beamof the electrons emitted from said cathode to saidplate, means for rotating said intensified beam of electrons in a closedtwo-dimensioned path substantially circular in form, a ring-shaped masklocated in said path between said cathode and said plate, said maskhaving a plurality of radially directed openings of varying areaslocated therein for correspondingly Varying the intensity of saidrotating beam of electrons projected upon said plate through saidopenings of said mask, said openings radially located in said mask intwo sequential series, the areas of the openings in each said seriesvarying progressively from an area of minimum value to an area ofmaximum value in accordance with a prescribed plan.

ANGELO MONTANI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,026,892 Heintz Jan. 7, 19362,071,382 Balsley Feb. 23, 1937 2,086,904 Evans July 13, 1937 2,173,193Zworykin Sept. 19, 1939

